1. Field of the Invention
The invention relates to the fabrication of an integrated circuit, and more particularly, to a lateral bipolar junction transistor (BJT) and a fabrication method thereof.
2. Description of Related Art
The transistor is a core device in the current electronic circuit. There are many types of transistors. Based on working principle, transistors can be divided into bipolar junction transistors (BJT) and field effect transistors (FET). BJTs are formed by a pn junction connected in opposite directions and have an emitter (E), a base (B), and a collector (C) as their three endpoints.
One of the main functions of BJTs is to serve as a switch, wherein there are two main uses. One is to switch a device having higher power; the other is to construct a digital logic circuit. Moreover, BJTs can amplify signals and have better power control, high-speed operation, and endurance ability, and are therefore frequently used to form amplifier circuits or to drive equipments such as speakers and electric motors, and are widely applied to the application products of aeronautics and space engineering, medical instruments, and robotics.
BJTs can also be applied to electrostatic discharge protection circuits. With the development of technology, the breakdown voltage of the current BJT is insufficient for the needs of the current device. For instance, in a process for making device operated between −VDD to 2.5VDD, the output swing is between −3.5 volts and 8.75 volts. It is difficult for traditional electrostatic discharge protection devices to satisfy the specified range. Moreover, the breakdown voltage of BJTs is only 7.7 volts, and therefore a BJT having a high breakdown voltage is needed.